RT Journal Article SR Electronic T1 Sample size and Markowitz diversification JF The Journal of Portfolio Management FD Institutional Investor Journals SP 18 OP 22 DO 10.3905/jpm.1983.408935 VO 10 IS 1 A1 Robert A. Olsen YR 1983 UL https://pm-research.com/content/10/1/18.abstract AB